Electrophotographic developing apparatus



March 26, 1957 E. c. GIAIMO, JR

ELECTROPHOTOGRAPHIC DEVELOPING APPARATUS Filed June 30. 1953 2 Sheets-Sheet l U w M fl X. I 4 w 1 N5 'E N TOR. Edward 61411110, :7

ATTORNEY March 26, 1957 E. c. GlAlMO, JR

ELECTROPHOTOGRAPHIC DEVELOPING APPARATUS Filed June 30, 1955 2 Sheets-Sheet 2 ATTORNEY United States Patent ELECTROPHOTOGRAPHIC DEVELOPING APPARATUS Edward C. Giaimo, Jr., Craubury, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application June 30, 1953, Serial No. 365,151

12 Claims. (Cl. 11851) The present invention relates to electrostatic printing and more particularly, although not necessarily exclusively to novel means for applying electroscopic developer material onto a surface bearing an electrostatic image.

In accordance with the present invention, a developer mix comprising a developer powder and a ferromagnetic carrier material is applied to a surface bearing a charge image in the presence of a magnetic field. A succession of magnetic fields arranged about the periphery of the drum is applied to a continuous member such as a paper sheet bearing a charge image. Means are provided for rotating the drum about its axis for sequentially presenting the aforesaid magnetic fields to said sheet member while the sheet member is being advanced. A quantity of developer mix comprising developer powder and a ferro-magnetic material is introduced in the field so that streamers are formed which constitute a brush like mass which brush over the surface of the charged image bearing member depositing the electroscopic developer powder upon that member in accordance with the charge pattern thereon.

An object of the present invention is to provide a novel means for applying eelctroscopic developer powder to a continuous charge-image bearing member.

It is another object of this invention to provide depositing means as set forth wherein the developer powder is applied by magnetically maintained brushes.

A further object is to provide depositing means as set forth wherein a supply of developer powder to the applying brushes may be continuously replenished and a new brush is formed following each application.

I Other objects and advantages of the present invention will become apparent to those skilled in the art from a reading of the following detailed description in connection with the accompanying drawing in which:

Fig, 1 is a plan view partly in section illustrating apparatus constructed in accordance with the present invention, and I Fig. 2 is a side elevation, partly schematic and partly in section, taken along the line 22 of Fig. 1 and looking in the direction of the appended arrows.

The apparatus to be described, embodying the invention in illustrative form, may be operated with a developer mix comprising a developer powder and a carrier material consisting of alcoholized iron, that is, iron particles free from grease and other impurities soluble in alcohol. These iron particles are preferably of rela tively small size, being in their greatest dimension about .002" to .008". Generally, any of the large number of developer powders known in the art is suitable for mixing with iron particles to form a developer mix to be employed in operating the present invention. A developer powder above iron in the triboelectric series is generally suitable for developing a direct image upon a negatively charged surface or a reversed image upon a positively charged surface, and conversely a developer powder below iron in the triboelectric series is suitable for developing a reversed image upon a like negatively ice charged surface or a direct image upon a positively charged surface. Example of the developer powders of the first named class are powdered shellac and rosin, each pigmented with a suitable coloring material such as carbon black. An example of the second class is Vinsol resin (an extract from long leave yellow pine stumps composed principally of an oxidized form of abietic acid and manufactured by Hercules Powder Company, 908 Market Street, Wilmington, Delaware) colored with a suitable dye such as azo oil black.

Developer mixes of the type described above for the sake of completeness of illustration and methods for employing such mixes are described and claimed in copending application of Harold G. Greig, Serial No. 344,123, filed March 23, 1953, and entitled Electrostatic Printing. An example of a suitable record receiving member of the kind referred to in the following description in a form of a sheet or web which is fully disclosed and claimed in a copending application of Harold G. Greig, Serial No. 248,937, filed September 9, 1951, now abandoned, and entitled Electrostatic Printing.

Referring, now, to the drawings in more detail, there is shown a first drum member 2 about which a continuous strip of charge image bearing paper 4 is partially wrapped. The paper is supplied from a supply roll 6 and, after treatment to be hereinafter described, may be wound up on a storage roll 8. This first drum comprises a relatively thin shell of non magnetic material.

Positioned adjacent to the first drum 2 is a second drum it). This second drum comprises a plurality of permanent magnets 12 arranged radially about the axis of the drum with all of the magnets having their corre sponding poles directed toward the axis. In the illustrative embodiment of the invention, four such permanent magnets are positioned at each end of the drum. A pole cap member 14 connects the outer extremities of corresponding magnet members 12 at opposite ends of the drum. The peripheral spaces between the pole cap members are closed by arcuate, non-magnetic filler members 16. The two ends of the drum are closed by end plate rnembers 18. The inner ends of the permanent magnets 12 are supported on soft iron hub members 20. Suitable axle members 22 are secured to the hub members and are journaled in bearing members 24-. Driving means such as an electric motor 25 is coupled to the drum 10 through the axle 22 to cause the drum to rotate about its axis.

The bearing members are carried by frame members 26 which also carry soft iron magnetic path defining means 28. The magnetic path defining means are magnetically coupled to the hub members 20 and are, accordingly, magnetically polarized by the permanent magnets 12. The magnetic path defining means 23 extends in two directions from the hub members Ztl. One leg 30 extends in a direction toward the first or paper carrying drum 2 and extends substantially beyond the periphery of the second drum. A flux concentrating backing bar 32 is magnetically coupled to the leg 30 and extends withing the first drum to provide a return path for magnetic return flux passing between the pole cap members 14 and the permanent magnets 12. Thus, a well defined magnetic fiux path is established between one of the pole cap members 14 and the backing bar 32 in the depositing area, substantially normal to the axes of the two drums. The other leg 34 of the soft iron path defining means 28 extends in adirection substantially diametrica 1y opposite from the first mentioned leg 30. This second leg extends only to the peripheral edge of the drum 1G and is magnetically coupled to the extremities of the pole cap member 14 which falls directly opposite the pole cap member which is adjacent the first drum in the depositing position. This arrangement effects a magnetic shunt substantially neutralizing the polarization of the pole cap coming under its influence.

About the periphery of the second drum and spaced therefrom, there is positioned a brass shell 3-5. Suitable openings are provided in this shell for purposes hereinafter set forth. On the outside of the brass shell is a similar shell 38 of magnetic material such as iron or magnetic steel. The shell 36 is supported by mounting panels 40 positioned adjacent the ends of the drum. These mounting panels 40 are also made of nozt-rnaguetizable material such as brass. The iron shell 33 is supported by the main frame members 26 which are of magnetizable material such as soft iron and are magnetically coupled to the permanent magnets 12 whereby the outer shell 38 is magnetized with a polarity that is opposite from the pole cap members 14. Such polarization of the outer shell establishes a magnetic flux, between the pole cap members and the outer shell, which is radial with respect to the drum. When magnetic particles are admitted to the system, the brush-like masses become attached to the pole cap members. The brass shell members assist in confining these brush-like masses.

A port 42 is provided through the two shell members. Through this port additional electroscopic powder or magnetic carrier or both may be added without interrupting the operation of the device. A second gap in the brass shell is provided in the lower side of the drum 10 remote from the first drum 2. In this gap, there is mounted a non-magnetic blade 44 with a non-magnetic shield member .6 attached thereto. On the outside of the blade and shield member, there is positioned a vibrator plate 48 which is pivoted about mounting screws 56 secured to the frame means 26. Suitable means 52, such as a solenoid, is provided to impart a vibratory motion to the vibrator plate 48.

In operation, the paper or other record member 4 leaves the supply roll 6 and passes through a charging and exposing station or position 54 where an electrostatic charge is imparted to the surface of the member, after which the charged member is exposed to a light image in accordance with a desired pattern to be recorded. As the paper leaves the charging and exposing station 54, it bears a chargeimage corresponding to the desired image to be recorded. As the paper is pulled about the first drum 2, the second drum is rotated in such a direction that the adjacent i peripheries travel in opposite directions as indicated by the arrows. The pole cap members 14 picl; up a mass of magnetic particles together with the intermixed electroscopic powder in the vicinity of the vibrator plate 48. As the drum 19 rotates, each pole cap member 14 carries its brush upward and into a brushing relationship with the charged surface of the paper carried by the first drum 2, depositing the electroscopic powder on the paper in accordance with the charge-image thereon. As the drum it continues to rotate in a clockwise direction, each pole cap member passes the port 42 where additional electroscopic powder may be added. Continuing the rotation of the drum it), the pole cap members come successively under the influence of the leg 34 of the magnetic path defining means 28. As each pole cap member is shunted, its field strength is reduced accordingly, permitting a substantial proportion of the magnetic particles constituting the brush-like mass to fall off. The remainder of the magnetic particles, which do not of themselves fall 01f, are removed by the passage of the pole cap member past the blade member 44. The removed magnetic particles, tog ther with the added electroscopic powder, fall onto and are caught by the vibrator plate 4-3. The vibratory motion imparted thereto by the vibrating means 52 causes the magnetic particles and the electroscopic powder to be thoroughly mixed and fed to the lower end of the vibrator plate. The shield member 45, attached to the blade 4-4, prevents the magnetic particles from being reattracted to the proximate pole cap member 14 as soon as that pole cap member passes from the zone of influence of the neutralizing leg 34 and before the particles have been thoroughly mixed by the action of the vibrator plate 48. After that pole cap member has passed beyond the extremity of the shield 46, a new brush-like mass of the thoroughly mixed particles is formed thereon, the new brush carrying a fresh supply of electroscopic powder. Thus, each time one of the pole cap members makes a revolution, there is a replenishing of the supply of electroscopic powder into the brush-like mass carried by the pole cap members. After the electroscopic powder has been brushed onto the charged surface of the image bearing member or paper 4, the paper is then passed through a fixing station or position 56 of suitable type well known in the art for causing the electroscopic powder to be permanently fixed. The finished copy may then be rolled up on the storage reel 8 or other suitable collecting means.

There has thus been provided an improved novel means for applying electroscopic developer powder to a continuous charge image bearing member wherein the powder is deposited by means of magnetically formed and maintained brush-like masses and wherein the supply of electroscopic powder to said applying brushes may be continuously replenished without interrupting the operation of the applying means.

What is claimed is:

1. Apparatus for depositing electroscopic developer powder onto a continuous member bearing an electrostatic charge image through the use of a developer mix including electroscopic developer powder and carrier particles of magnetic material, said apparatus comprising, in combination, means for moving the image bearing member past a depositing position, a plurality of magnetic field producing means, a rotatable drum, said field pro ducing means being arranged in spaced relation about the periphery of said drum for rotation therewith, and means for rotating said drum and thereby each of said field producing means sequentially past a quantity of the developer mix and then past said depositing position, said mix forming a brush-like mass adhering to each of said field producing means.

2. Apparatus for depositing electroscopic developer powder onto the surface of a continuous member bearing an electrostatic charge image through the use of a developer mix including electroscopic developer powder and carrier particles of magnetic material, said apparatus comprising, in combination, means for moving said image bearing member past a depositing position, a plurality of magnetic field producing means, a rotatable drum, said field producing means being arranged in spaced relation about the periphery of said drum for rotation therewith, means for rotating said drum and thereby each of said field producing means sequentially past a quantity of said mix and then past said depositing position, said mix forming a brush-like mass adhering to each of said field producing means, and flux concentrating means magnetically associated with said field producing means at said depositing position to define a flux path through said image bearing member.

3. Apparatus for depositing electroscopic developer powder onto the surface of a continuous member bearing an electrostatic charge-image through the use of a developer mix including electroscopic developer powder and carrier particles of magnetic material, said apparatus comprising, in combination, means for moving said image bearing member past a depositing position, a plurality of magnetic field producing means, a rotatable drum, said field producing means being arranged in spaced relation about the periphery of said drum for rotation therewith, means for rotating said drum and thereby each of said field producing means sequentially past a quantity of said mix and then past said depositing position, said mix adhering to each of said field producing means and forming a brush-like mass, and means for substantially removing said brush-like mass from said field producing means sub sequent to each passing of the depositing position,

4. Apparatus for depositing electroscopic developer powder onto the surface of a continuous member bearing an electrostatic charge-image through the use of a developer mix including an electroscopic developer powder and carrier particles of magnetic material, said apparatus comprising, in combination, means for moving said image bearing member past a depositing position, a plurality of magnetic field producing means, a rotatable drum, said field producing means being arranged in spaced relation about the periphery of said drum for rotation therewith, means for rotating said drum and thereby each of said field producing means sequentially past a quantity of said mix and then past said depositing position, said mix adboring to each of said field producing means and forming a brush-like mass, means whereby additional electroscopic powder may be added without interrupting the operation, means for substantially removing said brushlike mass from said field producing means subsequent to each passing of the depositing position, and means for collecting said removed brush-like mass and mixing said mass with said added powder.

5. The invention as set forth in claim 4 wherein said collecting and mixing means comprises a vibrator plate.

6. Apparatus for applying electroscopic developer powder to the surface of a continuous member bearing an electrostatic charge-image through the use of a developer mix including an electroscopic powder and carrier particles of magnetic material, said apparatus comprising, in combination, a first rotatable drum for moving said image bearing member past a depositing position, a second rotatable drum including a plurality of magnetic field producing means, said second drum being positioned adjacent to said first drum, said field producing means including a plurality of permanent magnet members, said magnet members being arranged radially with respect to said drum and in pairs, the members of said pairs being positioned at opposite ends of said drum, pole cap members joining the members of said pairs whereby to define a plurality of magnetic fields, a flux concentrating backing bar positioned within said first drum adjacent to said depositing position, said backing bar being magnetically coupled to said permanent magnet members to define a flux path through said image bearing member, magnetic shunt means associated with said field producing means at a neutralizing position remote from said depositing position, means for rotating said second drum and thereby each of said field producing means sequentially past a quantity of said mix to produce a brush-like mass adhering to said field producing means and then past said depositing position, and means including said shunt means at said neutralizing position for substantially removing said brush-like mass from said field producing means subsequent to each passing of the depositing position.

7. Apparatus for applying electroscopic developer powder to a continuous surface bearing an electrostatic charge image, said apparatus comprising, in combination, means for moving the image bearing member past a depositing position, a plurality of magnetic field producing means, a rotatable drum, said field producing means being arranged in spaced relation about the periphery of said drum for rotation therewith, and means for rotating said drum and thereby each of said field producing means sequentially past said quantity of mix and then past said depositing position, said mix forming a brush-like mass adhering to said field producing means.

8. Apparatus for applying electroscopic developer powder to a continuous surface bearing an electrostatic charge image thereon, said apparatus comprising, in combination, means for moving said image bearing member past a depositing position, 'a plurality of magnetic field producing means, a rotatable drum, said field producing means being arranged in spaced relation about the periphery of said drum for rotation therewith, flux concentrating means cooperatively associated with said field producing means at said depositing position to define a flux path through said image bearing member, field neutralizing means associated with said field producing means at a position remote from said depositing position, means to retain a quantity of developer mix including electroscopic developer powder and carrier particles of magnetic material, means for rotating said drum and thereby each of said field producing means sequentially past said retained quantity of mix to produce a brush-like mass adhering to said field producing means and then past said depositing position, and means including said neutralizing means for substantially removing said brush-like mass from said field producing means subsequent to each passing of the depositing position.

9. Apparatus for applying electroscopic developer powder to an electrostatic charge image bearing member, said apparatus comprising, in combination, a first rotatable drum for moving said image bearing member past a depositing position, a second rotatable drum including a plurality of magnetic field producing means, said second drum being positioned adjacent to said first drum, said field producing means including a plurality of permanent magnet members, said magnet members being arranged radially with respect to said drum and in pairs, the members of said pairs being positioned at opposite ends of said drum, the members of each of said pairs being joined by pole cap members whereby to define a plurality of magnetic fields, a flux concentrating backing bar positioned within said first drum adjacent to said depositing position, said backing bar being magnetically coupled to said permanent magnet members to define a flux path through said image bearing member, magnetic shunt means associated with said field producing means at a neutralizing position remote from said depositing position, a quantity of developer mix including electroscopic developer powder and carrier particles of magnetic material for mixing with developer powder to serve as a carrier therefor, means for rotating said second drum and thereby each of said field producing means sequentially past said quantity of mix to produce a brush-like mass adhering to said field producing means and then past said depositing position, and means including said shunt means at said neutralizing position for substantially removing said brush-like mass from said field producing means subsequent to each passing of the depositing position.

10. Apparatus for depositing electroscopic developer powder from a mixture of such powder and a quantity of magnetizable particles onto a member bearing an electrostatic charge image, said apparatus comprising means for supporting and advancing a member bearing an electrostatic charge image, magnetic field producing means for forming brush-like tufts of said mixture, means for moving said brush-like tufts into brushing contact with an image bearing member advanced by said first named means whereby to deposit said powder onto said member in the pattern of said image, and means for disrupting and reforming said brush-like tufts.

11. Apparatus for depositing electroscopic developer powder from a mixture of such powder and a quantity of magnetizable particles onto a member bearing a latent electrostatic charge image, said apparatus comprising means for supporting and advancing a member bearing an electrostatic charge image, magnetic field producing means for forming brush-like tufts of said mixture, means for moving said brush-like tufts into brushing contact with an image bearing member advanced by said first named means whereby to deposit said powder onto said member in the pattern of said image, and means for reducing the magnetic field produced by said field producing means to cause said brush-like tufts to be dropped subsequent to their brushing contact with said image bearing member.

12. Apparatus for depositing electroscopic developer powder from a mixture of such powder and a quantity of rnagnetizable particles onto a member bearing a latent electrostatic charge image, said apparatus comprising means for supporting and advancing a member bearing an electrostatic charge image, magnetic field producing means for forming brush-like tufts of said mixture, means for moving said brush-like tufts into brushing contact with an image bearing member advanced by said first named means whereby to deposit said powder onto said member in the pattern of said image, means for temporarily reducing the magnetic field produced by said field producing means to cause said particles to be dropped subsequent to their brushing contact with said image bearing member, and means for mixing said dropped particles with additional developer powder for formation into new brush-like tufts upon the reestablishment of said magnetic field.

References Cited in the file of this patent UNITED STATES PATENTS Fisher Feb. 16, Sanders et al. Dec. 22, Payne Jan. 9, Ullrich Sept. 3, Cousins Apr. 21, Neville Sept. 20, Canton Oct. 27, Osborne Apr. 29, Carlson Sept. 12, Walkup Nov. 18, Carlson Jan. 6, 

1. APPRATUS FOR DEPOSITING ELECTROSCOPIC DEVELOPER POWDER ONTO A CONTINUOUS MEMBER BEARING AN ELECTROSTATIC CHARGE IMAGE THROUGH THE USE OF A DEVELOPER MIX INCLUDING ELECTROSCOPIC DEVELOPER POWDER AND CARRIER PARTICLES OF MAGNETIC MATERIAL, SAID APPARATUS COMPRISING, IN, COMBINATION, MEANS FOR MOVING THE IMAGE BEARING MEMBER PASST A DEPOSIT ING POSITION, A PLURALITY OF MAGNETIC FIELD PRODUCING MEANS, A ROTATABLE DRUM, SAID FIELD PRODUCING MEANS BEING ARRANGED IN SPACED RELATION ABOUT THE PERIPHERY OF SAID DRUM FOR ROTATION THEREWITH, SAID MEANS FOR ROTATING SAID DRUM AND THEREBY EACH OF SAID FIELD PRODUCING MEANS SEQUENTIALLY PAST AQUANTITY OF THE DE- 